New approaches to the diagnosis of sepsis:

New approaches to sepsis: molecular diagnostics and biomarkers

Sepsis is among the most common causes of death in hospitals. It arises from the host response to infection. Currently, diagnosis relies on nonspecific physiological criteria and culture-based pathogen detection. This results in diagnostic uncertainty, therapeutic delays, the mis- and overuse of antibiotics, and the failure to identify patients who might benefit from immunomodulatory therapies. There is a need for new sepsis biomarkers that can aid in therapeutic decision making and add information about screening, diagnosis, risk stratification, and monitoring of the response to therapy. The host response involves hundreds of mediators and single molecules, many of which have been proposed as biomarkers. It is, however, unlikely that one single biomarker is able to satisfy all the needs and expectations for sepsis research and management. Among biomarkers that are measurable by assays approved for clinical use, procalcitonin (PCT) has shown some usefulness as an infection marker and for antibiotic stewardship. Other possible new approaches consist of molecular strategies to improve pathogen detection and molecular diagnostics and prognostics based on transcriptomic, proteomic, or metabolic profiling. Novel approaches to sepsis promise to transform sepsis from a physiologic syndrome into a group of distinct biochemical disorders and help in the development of better diagnostic tools and effective adjunctive sepsis therapies.

Activated partial thromboplastin time waveform analysis: a new tool to detect infection?

OBJECTIVE

An abnormality of the optical transmission waveform obtained during measurement of the activated partial thromboplastin time (aPTT) has been described to identify a high-risk intensive care unit population consisting of patients with sepsis or with higher mortality rates than patients with normal aPTT waveforms. We investigated the abnormal aPTT biphasic waveform as a diagnostic and prognostic marker of infection.

DESIGN

Prospective, observational study investigating the predictive value of aPTT waveform analysis for the diagnosis and prognosis of sepsis.

SETTING

Surgical intensive care unit of a university hospital.

PATIENTS

We studied 187 consecutive patients who fulfilled at least two or more criteria of the systemic inflammatory response syndrome at admission or during intensive care stay and classified as having systemic inflammatory response syndrome, sepsis, severe sepsis, or septic shock during an 8-month period.

INTERVENTIONS

Laboratory analyses including aPTT waveform analysis and procalcitonin and C-reactive protein concentrations were measured at days 1-3.

MEASUREMENTS AND MAIN RESULTS

The final diagnoses were systemic inflammatory response syndrome in 49%, sepsis in 16%, severe sepsis in 12%, and septic shock in 23% of patients. On day 1, the biphasic waveform was significantly more abnormal in patients with severe sepsis or septic shock than in patients with systemic inflammatory response syndrome or sepsis. The biphasic waveform was more accurate than procalcitonin and C-reactive protein for differentiating patients with severe sepsis and septic shock, with 90% sensitivity and 92% negative predictive value. Biphasic waveform values were significantly more abnormal during days 1-3 in septic nonsurvivors than in survivors and nonseptic nonsurvivors. The biphasic waveform exhibited the best specificity (91%) and negative predictive value (98%) for the prognosis of sepsis-related mortality on day 3.

CONCLUSIONS

In intensive care units, when the analyzer is available, aPTT waveform analysis is an inexpensive, rapid, effective, and readily available tool providing information for the diagnosis of severe sepsis and the prognosis of septic patients.

Plasma procalcitonin and C-reactive protein in acute septic shock: clinical and biological correlates

OBJECTIVE

To determine the relationship between plasma procalcitonin (PCT) levels, C-reactive protein (CRP), white blood cell count (WBC), ionized calcium (Ca2+), and patient outcome; and to compare the diagnostic and prognostic information provided by PCT and by CRP.

DESIGN

Prospective, observational study.

SETTING

Intensive care unit.

PATIENTS

Fifty-three patients with septic shock, consecutively diagnosed according to consensus guidelines.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood was sampled at diagnosis and 24 and 48 hrs later and in a subgroup (n = 23) after 120 hrs. PCT was measured with LUMItest and CRP with Vitros slides. Ca2+ was calculated according to McLean-Hastings from calcium and protein levels on Vitros. In all 53 patients, PCT and CRP were elevated (>0.5 ng/mL and >10 mg/L, respectively) within 24 hrs after diagnosis. Nonsurvivors (n = 25) were older (p <.001) and had higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores (p =.02) at diagnosis but did not differ in sepsis etiology, medical history, sex ratio, levels of PCT, CRP, and Ca2+, or WBC count at any time point. Using logistic regression, initial PCT levels were correlated with CRP values (p =.001) and APACHE II score (p <.05), but not with age, gender, Ca2+ levels, survival, or type of pathogen. Within 48 hrs, however, PCT levels decreased more frequently from baseline in survivors than in nonsurvivors (80% vs. 41%, p <.05). Likewise, CRP levels decreased more often in survivors (100% vs. 64%, p <.05) but only at 120 hrs.

CONCLUSIONS

PCT levels were correlated with the severity of disease at onset (APACHE II) and inflammation (CRP) but not with Ca2+ levels. Inaugural PCT or CRP levels per se poorly predicted outcome but decreasing levels were associated with a higher probability of survival. In this respect, PCT was found to be an earlier marker than CRP.